Biomass-derived epoxy compound and manufacturing method thereof

ABSTRACT

There is disclosed a biomass-derived epoxy compound as an epoxidized product of a raw-material biomass-derived compound having a weight-average molecular weight of 300 to 10000. The biomass-derived epoxy compound has a weight-average molecular weight of 600 to 20000 and is soluble in an organic solvent for the preparation of a varnish. The epoxy compound is prepared by dissolving the raw-material biomass-derived compound in an aqueous alkali solution; adding epichlorohydrin to the solution and heating the mixture; and evaporating epichlorohydrin from the heated mixture and precipitating a biomass-derived epoxy compound, in which the aqueous alkali solution has a pH of 13.5 to 11.0. The biomass-derived epoxy compound has both high solubility in organic solvents and satisfactory heat resistance and can be manufactured in a high yield on the basis of the raw material through a less number of processes.

CLAIM OF PRIORITY

The present application claims priority from Japanese Patent applicationserial No. 2008-326634, filed on Dec. 23, 2008, the content of which ishereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a biomass-derived epoxy compound andmanufacturing method thereof.

2. Description of Related Art

From the viewpoint of carbon neutrality, vegetable- or plant-derivedbiomass has been expected as materials that do not cause global warming.The use of such plant-derived biomass has been attempted in resins, ofwhich corn-derived thermoplastic poly(lactic acid)s have been mainlydeveloped for practical use.

The use of such corn-derived thermoplastic poly(lactic acid)s, however,has not been spreading recently, because they suffer from resourceconflict in the raw material corn with foodstuffs and they have lowheatproof temperatures.

Accordingly, the current mainstream is to develop resins which use, asraw materials, “inedible resources” not conflicting with foodstuff andare highly resistant to heat. Among such inedible resources, ligneouswastes, i.e., unutilized trees, abound in Japan are expected as rawmaterials for biomass-derived resins.

Specifically, lignins have highly thermally stable polyphenol skeletonsand are thereby expected to give biomass-derived thermosetting epoxycompounds, and these epoxy compounds in turn give epoxy resincompositions.

Lignins are plant-derived biomass and are firm or solid polymerscontaining propylphenols as backbone skeletons. Such lignins areclassified by the process of extracting from trees typically as alkalilignins, Klason lignins, and steam explosion lignins.

Exemplary plant-derived biomass further includes lignophenols. Thelignophenols have been prepared according to a technique of separatinglignocellulose materials into lignophenol materials and carbohydrates(Patent Literature 1 (Japanese Patent Laid-open No. Hei 09-278904)).This technique utilizes a phase separation system developed by Prof.Masamitsu FUNAOKA (Mie University). As a result of the separationthrough the phase separation system, lignins are combined with phenolsto give lignophenols. The resulting lignophenols are polyphenol resinsthat are linear molecules, have uniform structures, have a definitemelting point of about 130° C., and are highly soluble.

To apply to various products, an epoxy resin composition should havesatisfactory heat resistance properties and solubility. The solubilityis required for the epoxy resin composition to be dissolved in anorganic solvent to give a resin varnish, as described in PatentLiterature 2 (Japanese Patent Laid-open No. Hei 09-235349). A prepreg isprepared by impregnating a base material with the resin varnish anddrying the resulting article. Two or more plies of the prepreg arestacked, then thermally cured, and thereby yield products such ascopper-clad laminates or insulating layers of motors. If a resin varnishcontains an epoxy compound having insufficient solubility, it may oftengive a product unsatisfactory in properties such as heat resistanceproperties, because the ratio of the epoxy compound to a curing agent inthe resin varnish may vary.

According to a known epoxidation process of a phenol compound, an epoxycompound having satisfactory solubility is prepared by adding an aqueousalkali metal solution to a solution of the phenol compound inepichlorohydrin and refluxing the resulting mixture (Non-PatentLiterature 1 (H. Lee and K. Neville, “Handbook of Epoxy Resins”,McGraw-Hill, New York, 1960 pp. 2-3)). However, when a biomass-derivedphenol compound is epoxidized according to the known epoxidationprocess, the resulting epoxy compound is substantially insoluble inorganic solvents.

This is probably because the raw material biomass has a complicatedstructure including a wide variety of groups such as hydroxyl group,carboxyl group, carbonyl group, aldehyde group, and styryl group; analkali metal used in the known process acts upon these groups to causecleavage and re-polymerization of the material compound to thereby givean epoxy compound having an increased molecular weight; and theincreased molecular weight acts to reduce the solubility of the epoxycompound (Non-Patent Literature 2 (“Advanced Technologies for Chemicalsfrom Wood Resources”, CMC Publishing Co., Ltd., Tokyo Japan, 2007 pp.53-56)).

The uses of epoxidized lignins as biomass-derived epoxy compounds aredisclosed in Patent Literature 3 (Japanese Patent Laid-open No.2005-199209) and Patent Literature 4 (Japanese Patent Laid-open No.2006-066237).

Independently, the uses of epoxidized lignophenols as biomass-derivedepoxy compounds are disclosed in Non-Patent Literature 3 (“Technologiesfor Higher Functionalities and for Recycling of Plant-derived Plastics”Science & Technology Co., Ltd., Tokyo Japan, 2007 pp. 129) and PatentLiterature 5 (Japanese Patent Laid-open No. 2004-238539).

All these documents, however, fail to describe how to preventbiomass-derived epoxy compounds from increasing in molecular weight andhow to allow them to have high solubility in organic solvents.

SUMMARY OF THE INVENTION

Epoxy resin compositions for the manufacturing of products each containsuch an epoxy compound and a curing agent.

If lignins and lignophenols as biomass resources are epoxidizedaccording to the known process, they give epoxy compounds having anincreased molecular weight and thereby showing remarkably poorsolubility in organic solvents. The biomass-derived resin compositionscontaining these epoxidized compounds and curing agents are difficult tobe formulated into varnishes and, therefore, difficult to be applied toproducts.

Under these circumstances, we have made intensive investigations on thetechnique of controlling or specifying the molecular weight of abiomass-derived epoxy compound so that the biomass-derived epoxycompound can be readily formulated into a varnish. Even this technique,however, suffers from some problems. Typically, the yield of thebiomass-derived epoxy compound is low relative to the material biomass,and the production of the biomass-derived epoxy compound needs a largernumber of processes.

Accordingly, an object of the present invention is to provide abiomass-derived epoxy compound that has both high solubility and highheat resistance properties. Another object of the present invention isto provide a method that can manufacture the biomass-derived epoxycompound in a high yield on the basis of the raw material through asmaller number of processes.

Yet another object of the present invention is to provide, for example,an epoxy resin composition, such as a varnish, adhesive, or coatingmaterial, using the biomass-derived epoxy compound; a copper-cladlaminate using them as a prepreg or insulating layer; and a motorproduct (electrical rotating machinery) using them.

Specifically, in an embodiment, the present invention provides abiomass-derived epoxy compound prepared through epoxidation of araw-material biomass-derived compound having 300 to 10000 in aweight-average molecular weight, in which the biomass-derived epoxycompound after the epoxidation has 600 to 20000 in the weight-averagemolecular weight and is soluble in an organic solvent for preparing avarnish.

The biomass-derived epoxy compound according to the present inventionhas both high solubility in an organic solvent and satisfactory heatresistance properties and can be manufactured in a high yield on thebasis of the raw material through a smaller number of processes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a ball gridarray according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to biomass-derived epoxy compounds thatare prepared from raw-material plant-derived biomass (biomass-derivedcompounds) and are highly soluble in organic solvents and to epoxy resincompositions which use the biomass-derived epoxy compounds and arehighly thermally stable.

When biomass-derived epoxy compounds are prepared through epoxidation ofraw-material lignins and lignophenols as biomass-derived compoundsaccording to the known techniques, their molecular weights(weight-average molecular weights) are ten times as high as those of theraw materials. The biomass-derived epoxy compounds are thereby sparinglysoluble in organic solvents. Biomass-derived epoxy resin compositionscontaining the biomass-derived epoxy compounds are difficult to beformulated into varnishes as solutions in organic solvents andtherefore, difficult to be applied to products.

As is described above, the biomass-derived epoxy resin compositionsprepared through epoxidation according to the known techniques haveweight-average molecular weights ten times as high as those of thematerial compounds. To avoid problems caused by such high molecularweights, fractions having relatively high molecular weights have beenseparated and removed from the biomass-derived compounds, and onlyfractions having relatively low molecular weights have been used as rawmaterials. Accordingly, only very small portions of the biomass-derivedcompounds have been usable as raw materials.

In contrast, we have made investigations specifically to provide such amethod for synthesizing (method for manufacturing) a biomass-derivedepoxy compound as to achieve a ratio Mw′/Mw of 2 or less, where Mw′represents the weight-average molecular weight of a synthesized(epoxidized) biomass-derived epoxy compound; and Mw represents theweight-average molecular weight of a raw-material biomass(biomass-derived compound).

In the investigations on the method, we have also made aim at notincreasing the number of manufacturing processes and at providing abiomass-derived epoxy compound being highly soluble in organic solvents.

The present invention will be described in detail below.

The biomass-derived epoxy compound according to an embodiment of thepresent invention is prepared through epoxidation of a raw-materialbiomass-derived compound, has a weight-average molecular weight Mw′ of600 to 20000, and is soluble in an organic solvent for the preparationof a varnish.

Exemplary biomass-derived compounds include lignins, lignophenols,soybean oils, and castor oils.

The weight-average molecular weight Mw of the raw materialbiomass-derived compound before epoxidation preferably ranges from 300to 10000. If a biomass-derived compound has a weight-average molecularweight Mw less than 300, it may not give a biomass-derived epoxycompound having sufficiently high heat resistance properties, becausesuch biomass-derived compound does not contain hydroxy group (OH group),aldehyde group (CHO group), and carboxyl group (COOH group) in asufficient number. In contrast, if a biomass-derived compound has aweight-average molecular weight Mw more than 10000, it may give abiomass-derived epoxy compound having a weight-average molecular weightMw′ more than 20000 and being less soluble in organic solvents for thepreparation of resin varnishes.

The weight-average molecular weight Mw′ is more preferably more than1200 and 20000 or less, from the viewpoint of providing sufficient heatresistance properties and satisfactory solubility. It is furthermorepreferably more than 12000 and 20000 or less, when high heat resistanceproperties are particularly needed.

An epoxy resin composition according to another embodiment of thepresent invention includes the biomass-derived epoxy compound and atleast one curing agent.

The curing agent in the epoxy resin composition preferably includes abiomass-derived compound.

An epoxy resin varnish according to yet another embodiment of thepresent invention includes at least one organic solvent and the epoxyresin composition dissolved in the organic solvent, in which the epoxyresin composition is present at a concentration of 10 to 90 percent byweight.

The organic solvent in the epoxy resin varnish may be at least oneselected typically from alcohols, carbonyl compounds, and aromaticcompounds.

Exemplary alcohols for use in the epoxy resin varnish include2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, and2-butoxyethanol. Exemplary carbonyl compounds include methyl ethylketone, isobutyl ethyl ketone, cyclohexanone, γ-butyrolactone, andN,N-dimethylformamide; and exemplary aromatic compounds include tolueneand xylenes.

A prepreg according to an embodiment of the present invention isprepared by impregnating a base material with the epoxy resin varnishand drying the resulting article.

The prepreg can be used for the manufacture typically of printed circuitboards, electronic devices and electrical rotating machineries.

A method for manufacturing a biomass-derived epoxy compound, accordingto an embodiment of the present invention, includes reacting araw-material biomass-derived compound with epichlorohydrin in an aqueousalkali solution, in which the aqueous alkali solution has a pH of 13.5to 11.0.

The aqueous alkali solution for use in the method may be selectedtypically from aqueous organic ammonium solutions, aqueous alkalineearth metal salt solutions and aqueous carbonate solutions.

Exemplary aqueous organic ammonium solutions include aqueous solutionsof tetraalkylammonium hydroxides. Exemplary tetraalkylammoniumhydroxides include tetramethylammonium hydroxide, tetraethylammoniumhydroxide, tetrapropylammonium hydroxide, and tetrabutylammoniumhydroxide. Each of different tetraalkylammonium hydroxides may be usedalone or in combination.

Examples of the carbonates include sodium carbonate, potassiumcarbonate, and calcium carbonate.

The biomass-derived curing agents are compounds having hydroxy group (OHgroup), aldehyde group (CHO group), and/or carboxyl group (COOH group),and specific examples thereof include steam explosionlow-molecular-weight lignins, alkali lignins, Klason lignins andlignophenols.

The weight-average molecular weight Mw before epoxidation preferablyranges from 300 to 10000. If a material biomass-derived compound has aweight-average molecular weight Mw less than 300, it may contain OHgroup, CHO group and carboxyl group in insufficient numbers and maythereby give a biomass-derived epoxy compound having unsatisfactory heatresistance properties. In contrast, if a material biomass-derivedcompound has a weight-average molecular weight Mw more than 10000, itmay give a biomass-derived epoxy compound having insufficient solubilityin organic solvents through epoxidation.

The weight-average molecular weight Mw is more preferably more than 1200and 10000 or less from the viewpoint of providing sufficient heatresistance properties and satisfactory solubility.

If a varnish contains an undissolved epoxy resin composition(undissolved biomass-derived epoxy compound), the ratio of thebiomass-derived epoxy compound to the curing agent partially deviatesfrom the stoichiometric ratio, and this may cause a cured articleprepared from the varnish to be unsatisfactory in properties such asheat resistance properties, stability, and resistance to waterabsorption (water-blocking properties). Therefore, the biomass-derivedepoxy compound should be soluble in an organic solvent for thepreparation of a varnish.

Petroleum-derived epoxy compounds and petroleum-derived curing agentshave definite chemical structures. The epoxy resin composition furthercontaining these epoxy compounds and/or curing agents can control itsproperties easily. In addition, most of such petroleum-derived epoxycompounds and petroleum-derived curing agents are satisfactorily solublein organic solvents.

Petroleum-derived epoxy compounds and petroleum-derived curing agentsfor use herein preferably have satisfactory solubility and sufficientheat resistance properties. Specific examples of petroleum-derived epoxycompounds include bisphenol-A epoxy compounds, bisphenol-F glycidylether epoxy compounds, bisphenol-S glycidyl ether epoxy compounds,bisphenol-AD glycidyl ether epoxy compounds, phenol-novolac epoxycompounds, cresol-novolac epoxy compounds, and3,3′,5,5′-tetramethyl-4,4′-dihydroxybiphenylglycidyl ether epoxycompounds although they are not limited to the above compounds. Theepoxy compounds preferably contain minimum amounts of ionic substancessuch as Na⁺ and Cl⁻.

Exemplary petroleum-derived curing agents for use herein include amineswith linear structure, alicyclic amines, aromatic amines, other amineswith cyclic structure, modified amines, acid anhydrides (e.g., maleicanhydride), polyhydric phenol curing agents, bisphenol curing agents,polyphenol curing agents, novolac phenol curing agents, andalkylene-modified phenol curing agents. Each of differentpetroleum-derived curing agents may be used alone or in combination. Thecuring agents preferably contain minimum amounts of ionic substancessuch as Na⁺ and Cl⁻.

Where necessary, the epoxy resin composition may further contain one ormore of known curing accelerators generally used as catalysts. Each ofthe different catalysts (curing accelerators) can be used alone or incombination. Exemplary curing accelerators include tertiary aminecompounds, imidazoles, organic sulfines, phosphorus compounds, salts oftetraphenylboron, and derivatives of them. The amount of curingaccelerators is not especially limited, as long as being such an amountas to exhibit a curing-accelerating activity.

Where necessary, the epoxy resin composition may further contain one ormore of known coupling agents. Each of the different coupling agents maybe used alone or in combination. Exemplary coupling agents includeepoxysilanes, aminosilanes, ureidosilanes, vinylsilanes, alkylsilanes,organic titanates, and aluminum alkylates.

The epoxy resin composition may further contain one or more flameretardants. Exemplary flame retardants include phosphorus-containingcompounds (including elementary phosphorus), such as red phosphorus(amorphous phosphorus), phosphoric acid and phosphoric acid esters;nitrogen-containing compounds such as melamines, melamine derivatives,triazine-ring-containing compounds, cyanuric acid derivatives andisocyanuric acid derivatives; phosphorus-nitrogen-containing compoundssuch as cyclophosphazenes; metallic compounds such as zinc oxide, ironoxide, molybdenum oxide and ferrocene; antimony oxides such as antimonytrioxide, antimony tetroxide and antimony pentaoxide; and brominatedepoxy resins. Each of different flame retardants may be used alone or incombination.

The epoxy resin composition may further contain one or more inorganicfillers generally used. Such inorganic fillers are used for the purposetypically of improving properties such as hygroscopicity (moistureabsorption), thermal conductivity and strength, and/or reducingcoefficient of thermal expansion. Exemplary fillers include powderysubstances typically of fused silica, crystalline silica, alumina,zircon, calcium silicate, calcium carbonate, potassium titanate, siliconcarbide, silicon nitride, aluminum nitride, boron nitride, beryllia(beryllium oxide), zirconia, zircon, fosterite, steatite, spinel,mullite, and titania; beads prepared from these powders; and glassfibers.

Exemplary inorganic fillers having flame retardancy further includealuminum hydroxide, magnesium hydroxide, zinc silicate, zinc molybdateand the like. Each of different inorganic fillers may be used alone orin combination.

The epoxy resin composition may further contain one or more otherresins, one or more catalysts for the acceleration of reaction and/orone or more additives according to necessity. Exemplary additivesinclude flame retardants, leveling agents and defoaming agents.

The epoxy resin composition may further contain one or more ion trappers(ion scavengers) for improving properties of product electronic devices,such as moisture resistance and properties at high temperature (heatresistance properties). The ion trappers for use herein are notespecially limited in their type, and can be any of known ion trappersor ion scavengers. Exemplary ion trappers include hydrotalcites; andhydrous oxides of elements such as magnesium, aluminum, titanium,zirconium and bismuth. Each of different ion trappers may be used aloneor in combination.

The epoxy resin composition may further contain other additivesaccording to necessity. Exemplary other additives herein includestress-relaxing agents such as silicone rubber powders; colorants suchas dyestuffs and carbon blacks; leveling agents; and defoaming agents.

The epoxy resin composition may be prepared by mixing components(materials) according to any process or device, as long as thecomponents (materials) can be uniformly dispersed in and mixed with oneanother. In general, the composition is prepared by weighingpredetermined amounts of the materials, and dispersing and mixing themwith one another typically using a device such as ball mill, triple rollmill, vacuum masher, pot mill or hybrid mixer.

The epoxy resin composition containing the biomass-derived epoxycompound as a component shows high solubility in organic solvents andsatisfactory heat resistance properties and can thereby give productswith remarkably improved reliability.

When used in the preparation of a copper-clad laminate, the epoxy resincomposition should be dissolved in a solvent (organic solvent), becausethe preparation essentially includes a step of impregnating a glasscloth with a varnish of the epoxy resin composition.

The epoxy resin composition is also satisfactorily formable (moldable)by hot forming. Typically, when an epoxy resin composition is formulatedinto an encapsulant, and the encapsulant is charged into gaps (100 μmgaps) in a flip-chip packaged ball grid array (FC-BGA) according to acapillary flow method, if the epoxy resin composition has insufficientformability, it may cause encapsulation failure at corner edges of thechip and bubble entrainment, and this may lead to deterioration inreliability of the resulting semiconductor device.

Exemplary products in which the epoxy resin composition is used includecopper-clad laminates each using a prepreg prepared from the epoxy resincomposition; computers and cellular phones including the copper-cladlaminates; motors whose coil unit is insulated by the prepreg; andindustrial robots and rotating machineries including the motors.Exemplary products further include chip-size packages in which devicesare encapsulated with the encapsulant using the epoxy resin composition;and adhesives and coating materials (paints) using the biomass-derivedepoxy resin composition.

The present invention will be illustrated in further detail withreference to several examples and comparative examples below. It shouldbe noted, however, that these examples are never construed to limit thescope of the present invention.

Test materials used in the examples are shown below by a trade name orabbreviation.

Low-molecular-weight lignin: Lignin derived from raw-material Cedarlignin, having a weight-average molecular weight Mw of 1500, and havinga hydroxyl equivalent of 400 g/eq

Lignophenol: One having a weight-average molecular weight Mw of 4400 andhaving a hydroxyl equivalent of 160 g/eq (supplied by TOYO JUSHICORPORATION)

HP 850: o-Cresol-novolac resin having an epoxy equivalent of 106 g/eq(supplied by Hitachi Chemical Co., Ltd.)

P-200: Imidazole curing catalyst (supplied by Japan Epoxy Resins Co.,Ltd.)

KBM 403: Coupling agent (γ-glycidoxypropyltrimethoxysilane; supplied byShin-Etsu Chemical Co., Ltd.)

JER 828: Bisphenol-A epoxy resin, having an epoxy equivalent of 190 g/eq(supplied by Japan Epoxy Resins Co., Ltd.)

RE 404S: Bisphenol-F epoxy resin, having an epoxy equivalent of 165 g/eq(supplied by Nippon Kayaku Co., Ltd.)

KAYAHARD AA: 4,4′-Methylenebis(2-ethylaniline) (supplied by NipponKayaku Co., Ltd.)

MHAC-P: Methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride,having a weight-average molecular weight Mw of 178 (supplied by HitachiChemical Co., Ltd.)

Tests were conducted according to the following methods.

Test Methods

(a) Solubility

The solubility of a sample epoxidized biomass (biomass-derived epoxycompound) was tested by visually observing how the biomass-derived epoxycompound was dissolved at a concentration of 50 percent by weight in a1:1 (by weight) solvent mixture of 2-methoxyethanol and methyl ethylketone. A sample fully dissolved in the solvent mixture was evaluated ashaving good solubility (Good), and one partially insoluble in thesolvent mixture was evaluated as having poor solubility (Poor).

(b) Weight-Average Molecular Weight

The weight-average molecular weight (in terms of polystyrene) of asample was measured using the detector Model L-4000 (UV detector; 270nm) supplied by Hitachi Chemical Co., Ltd. under the followingconditions:

Column: Two Gelpak GL-S300MDT-5 columns

Column temperature: 30° C.

Flow rate: 1.0 mL per minute

Eluent: DMF/THF=1/1 (1) plus 0.06 M phosphoric acid plus 0.06 M LiBr,wherein DMF represents N,N-dimethylformamide; and THF representstetrahydrofuran.

(c) Epoxy Equivalent

The epoxy equivalent of a sample was measured in accordance with themethod specified in Japanese Industrial Standards (JIS) K 7236 (thepyridine hydrochloride method).

(d) Hydroxyl Equivalent

The hydroxyl equivalent of a sample was measured in accordance with themethod specified in JIS K 6755.

(e) Detection of Epoxidation

The ¹H-NMR spectrum of a sample epoxidized product (biomass-derivedepoxy compound) was measured using deuterated dimethyl sulfoxide as asolvent, and the presence of protons derived from introduced epoxy groupwas detected from peaks at 2.6 ppm and 2.8 ppm. In addition, thepresence of epoxy group was further detected from the presence of anabsorption at 910 cm⁻¹ in a Fourier transform infrared spectroscopy(FT-IR).

(f) Glass Transition Temperature (Tg)

The glass transition temperature (Tg) of a sample was determined in thefollowing manner. Each of the compositions according to Examples 5 to 11and Comparative Example 5 as given in Table 1 was cured at temperaturesranging from room temperature to 250° C. for one hour to give a film 100μm thick. The storage modulus E′ and loss modulus E″ of the film weremeasured using a dynamic mechanical analyzer (DMA) while raising thetemperature at a rate of 5° C. per minute, from which tangent delta (tanδ was determined as the ratio of the loss modulus E″ to the storagemodulus E′, and the glass transition temperature (Tg) was determinedfrom the peak temperature of tan δ.

(g) Shear Strength

A cured article (as a block) having a length of 4 mm, a width of 4 mmand a thickness of 1 mm was formed from a sample epoxy resin on asubstrate made of a negative-working photosensitive polyimide (suppliedby HD MicroSystems, Ltd., under the trade name PL-H708); the adhesivestrength under shear (longitudinal shear strength) between thephotosensitive polyimide and the epoxy resin cured article was measuredusing the Multi-purpose Bondtester (Dage, Model PC 2400) to evaluateadhesive properties. In the measurement, a shearing tool was fixed 50 μmabove the photosensitive polyimide substrate, and the shear strength wasmeasured at a tool speed of 300 μm per second.

(h) Resistance to Soldering Heat

The resistance of a sample copper-clad laminate to soldering heat (heatapplied upon soldering) was measured in accordance with the test methodspecified in JIS C 6481. Specifically, according to the test method, asample copper-clad laminate 50 mm thick was prepared, the copper cladwas etched, the resulting article was placed in boiling distilled waterfor one hour to absorb water and was immersed in a bath of molten solderat 260° C. for three minutes, and whether peeling occurred or not wasdetermined.

(i) Volume Resistivity

The volume resistivity of a sample was measured in accordance with JIS C6481 at 25° C.

(j) Peel Strength

The peel strength of the copper clad was measured in accordance with JISC 6481.

Some examples will be described below.

EXAMPLE 1

In a 2-liter four-neck flask equipped with stirring blades, a condenserand a thermometer were placed 100 grams of a low-molecular-weight ligninand 300 grams of a 10% aqueous tetramethylammonium hydroxide solution,followed by stirring for 30 minutes to give a solution.

The solution was further combined with 300 grams of epichlorohydrin, andthe mixture was heated under reflux on an oil bath at 120° C. for onehour. The reaction mixture was cooled to room temperature, placed in aseparating funnel, and washed with pure water until the oil layer becameneutral.

After removing water therefrom, the residue was combined with 50 gramsof a 20% aqueous tetramethylammonium hydroxide solution and heated underreflux at 120° C. for one hour, followed by washing with water.

This was placed in a rotary evaporator, from which about 80% ofepichlorohydrin, water and by-products were evaporated and removed, theresidue was placed in 2 liters of ethyl alcohol and thereby yieldedwhite precipitates.

Ethyl alcohol was used herein, but another alcohol such as methylalcohol, propyl alcohol, butyl alcohol, pentyl alcohol or hexyl alcoholmay be used.

The precipitates were collected by filtration, dried in vacuo, andthereby yielded an epoxidized low-molecular-weight lignin EL1.

The epoxidized low-molecular-weight lignin EL1 gave peaks at 2.6 ppm and2.8 ppm through proton nuclear magnetic resonance spectroscopy (¹H-NMR)and gave an absorption at 914 cm⁻¹ through FT-IR, verifying that epoxygroups have been introduced (added) to lignin.

The epoxidized low-molecular-weight lignin EL1 according to this examplewas prepared in a yield of 106 grams and had a weight-average molecularweight Mw′ of 2800. This was satisfactorily dissolved in an equivalentweight of 2-methoxyethanol (2MOE). The aqueous tetramethylammoniumhydroxide solution had a pH of 12.9. As used herein “pH” refers to ahydrogen ion concentration.

EXAMPLE 2

An epoxidized low-molecular-weight lignin EL2 was prepared throughsynthesis by the procedure of Example 1, except for using an aqueoustetraethylammonium hydroxide solution having a pH of 12.6. EL2 wasprepared in a yield of 104 grams, had a weight-average molecular weightMw′ of 2590, and was soluble in 2MOE. The introduction of epoxy groupsinto lignin was confirmed through ¹H-NMR and FT-IR analyses.

EXAMPLE 3

An epoxidized low-molecular-weight lignin EL3 was prepared throughsynthesis by the procedure of Example 1, except for using an aqueouspotassium carbonate solution having a pH of 11.6. EL3 was prepared in ayield of 110 grams, had a weight-average molecular weight Mw′ of 2900,and was soluble in 2MOE. The introduction of epoxy groups into ligninwas confirmed through ¹H-NMR and FT-IR analyses.

EXAMPLE 4

An epoxidized lignophenol ELP1 was prepared through synthesis by theprocedure of Example 1, except for using a lignophenol and an aqueouscalcium carbonate solution having a pH of 11.8. ELP1 was prepared in ayield of 102 grams, had a weight-average molecular weight Mw′ of 7600,and was soluble in 2MOE. The introduction of epoxy groups intolignophenol was confirmed through ¹H-NMR and FT-IR analyses.

COMPARATIVE EXAMPLE 1

In a 2-liter four-neck flask equipped with stirring blades, a condenserand a thermometer were placed 100 grams of a low-molecular-weight ligninand 300 grams of a 10% aqueous sodium hydroxide solution, followed bystirring for 30 minutes to give a solution.

The solution was further combined with 300 grams of epichlorohydrin,followed by heating under reflux at 92° C. for one hour.

The reaction mixture was cooled to room temperature, placed in aseparating funnel, and washed with pure water until the oil layer becameneutral. After removing water therefrom, the residue was combined with30 grams of a 10% aqueous sodium hydroxide solution and reacted at 92°C. for one hour, followed by refluxing and washing with water. Afterremoving about 800 of epichlorohydrin, water and by-products, theresidue was placed in 2 liters of ethanol to give white precipitates.

The precipitates were collected by filtration, dried in vacuo, andthereby yielded an epoxidized lignin ELh1. The introduction of epoxygroups in ELh1 was confirmed through ¹H-NMR and FT-IR analyses. Theepoxidized lignin ELh1 was prepared in a yield of 106 grams, but itsweight-average molecular weight Mw′ could not be measured, because itwas insoluble in tetrahydrofuran or N,N-dimethylformamide used as asolvent for gel permeation chromatography (GPC). This was also insolublein 2MOE. The 10% aqueous sodium hydroxide solution has a pH of 14.0.

COMPARATIVE EXAMPLE 2

An epoxidized lignin ELh2 was prepared by carrying out epoxidation underthe same conditions as in Comparative Example 1, except for carrying outa reaction for the introduction of epoxy groups (epoxidation) at 45° C.and a pressure of 95 mmHg for half an hour (0.5 hour). The introductionof epoxy groups in ELh2 was confirmed through ¹H-NMR and FT-IR analyses.ELh2 was prepared in a yield of 105 grams, but its weight-averagemolecular weight Mw′ could not be measured, because it was insoluble intetrahydrofuran or N,N-dimethylformamide. This was also insoluble in2MOE.

COMPARATIVE EXAMPLE 3

An epoxidized lignophenol ELPh3 was prepared by carrying out epoxidationunder the same conditions as in Comparative Example 2, except for usinga lignophenol as the biomass compound. The introduction of epoxy groupsin ELPh3 was confirmed through ¹H-NMR and FT-IR analyses. ELPh3 wasprepared in a yield of 106 grams, but its weight-average molecularweight Mw′ could not be measured, because it was insoluble intetrahydrofuran or N,N-dimethylformamide. This was also insoluble in2MOE.

COMPARATIVE EXAMPLE 4

An epoxidized lignin ELh4 was prepared by the procedure of ComparativeExample 1, except for using a low-molecular-weight lignin and an aqueoussodium carbonate solution having a pH of 10.9, and carrying out anepoxidation reaction at 92° C. for 2 hours. ELh4 was prepared in a yieldof 106 grams and had a weight-average molecular weight Mw′ of 1600. ELh4was soluble in 2MOE, but the introduction of epoxy groups thereinto wasnot confirmed by ¹H-NMR and FT-IR analyses.

The data obtained in Examples 1 to 4 and Comparative Examples 1 to 4demonstrate that, when low-molecular-weight lignins and lignophenols areused as raw-material biomass-derived compounds, the weight-averagemolecular weights Mw′ of the resulting epoxy compounds fall within twicethe weight-average molecular weights Mw of the raw materials, and theproduct epoxy compounds show less increase in molecular weight and excelin solubility, when prepared by using an aqueous alkali solution havinga pH ranging from 13.5 to 11.0.

In Comparative Examples 1 to 3 using an aqueous sodium hydroxidesolution having a pH of 14.0, the epoxidation of the prepared productswas confirmed through ¹H-NMR and FT-IR analyses, but theirweight-average molecular weights Mw′ could not be measured, because theywere insoluble in N,N-dimethylformamide or tetrahydrofuran. This isprobably because the products gained higher molecular weights andpartially underwent a crosslinking reaction during the epoxidationreaction.

In Comparative Example 4 using a weakly alkaline aqueous sodiumcarbonate solution having a pH of 10.9, the product showed goodsolubility but the introduction of epoxy groups (epoxidation) was notconfirmed through ¹H-NMR, indicating that epoxidation was insufficient.

Next, the prepared products were formulated into varnishes, copper-cladlaminates were prepared using the varnishes, and properties of thecopper-clad laminates were tested.

EXAMPLES 5 TO 11

Properties of Copper-Clad Laminates Prepared Using Varnishes of EpoxyResin Compositions

In Example 5, a varnish of epoxy resin composition was prepared byadding a stoichiometric amount of a low-molecular-weight lignin as acuring agent to the epoxidized lignin EL1, where EL1 was prepared inExample 1, had a weight-average molecular weight Mw′ of 2800 and had anepoxy equivalent of 395 g/eq; further adding 0.5 percent by weight ofP-200 (catalyst) relative to the amount of the epoxy resin composition;and adding a 1:1 (by weight) solvent mixture of 2-methoxyethanol andmethyl ethyl ketone so as to give a resin concentration of 50 percent byweight.

In Examples 6 to 11, varnishes were prepared by the procedure of Example5, except for using components such as epoxy compound, curing agent, andcuring catalyst given in Table 1. As the organic solvent, the solventmixture as with Example 5 was used.

Glass clothes each 30-cm square and 100 μm thick were impregnated witheach varnish of epoxy resin composition, heated in a hot-air oven at130° C. for eight minutes so as to allow the epoxy resin composition tobe in an intermediate curing stage (B-stage), and thereby yielded sixplies of non-sticky prepregs. The six plies were laid on one another togive a laminate, the laminate was sandwiched between two plies of copperfoil each 35 μm thick, heated using a vacuum press at a heating rate of6° C. per minute to 220° C., further held at 220° C. for one hour forcomplete curing (C-stage), and thereby yielded copper-clad laminateswithout defects.

The compositions and properties of the copper-clad laminates prepared inExamples 5 to 11 are shown in Table 1, in which the abbreviation “828”refers to “JER 828”.

COMPARATIVE EXAMPLE 5

The resin composition according to Comparative Example 5 also given inTable 1 could not be formulated into a varnish, and a layer formed fromthe resin composition used as intact in the test for resistance tosoldering heat was peeled off due to its low peel strength.

TABLE 1 Properties of Epoxy Resin Composition Varnishes and Copper-cladLaminates Curing catalyst Properties Epoxy (0.5 percent by Tg PeelResistance to Number compound Curing agent weight) Solubility* (° C.)strength soldering heat Example 5 EL1 Low-molecular lignin P-200 Good220 1.4 Good Example 6 EL2 Low-molecular lignin P-200 Good 245 1.3 Goodand MHAC-P Example 7 EL3 HP 850 P-200 Good 260 1.4 Good Example 8 EL1and 828 KAYAHARD AA none Good 230 1.3 Good Example 9 ELP1 LP P-200 Good240 1.4 Good Example 10 ELP1 LP and HP 850 P-200 Good 225 1.4 GoodExample 11 ELP1 and 828 none P-200 Good 200 1.2 Good Comparative ELPh3HP 850 P-200 Poor 180 0.6 Poor Example 5 *1:1 (by weight) mixture of2-methoxyethanol and methyl ethyl ketone LP: Lignophenol

EXAMPLE 12

(Resin Encapsulants)

A series of resin encapsulants were prepared by kneading epoxy resincompositions using a three-roll mill and a vacuum masher. Theircompositions are as follows.

Initially, 45 grams of RE 404S (bisphenol-F epoxy resin; supplied byNippon Kayaku Co., Ltd., having an epoxy equivalent of 165 g/eq), 55grams of ELL and 120 grams of a lignin were mixed, and the mixture wasfurther combined with 0.5 percent by weight of the catalyst P-200 and 2percent by weight of the coupling agent KBM 403 relative to the totalamount of the epoxy resin composition.

The mixture was further combined with 1.0 percent by weight of an iontrapper (ion scavenger) IWE 500 (supplied by Toagosei Co., Ltd.) andthereby yielded an epoxy resin composition A.

Next, three types of high-purity spherical fillers were mixed, themixture was added in an amount of 50 percent by volume to the epoxyresin composition A and thereby yielded a resin encapsulant A. The threetypes of high-purity spherical fillers were SP-4B (supplied by FusoChemical Co., Ltd., having an average particle diameter of 5.1 μm),QS4F2 (supplied by Mitsubishi Rayon Co., Ltd., having an averageparticle diameter of 4.6 μm), and SO25R (supplied by Tatsumori Ltd.,having an average particle diameter of 0.68 μm).

The resin encapsulant A had a glass transition temperature Tg of 180° C.and a shear strength of 8.8 MPa.

A resin encapsulant B was prepared by the procedure as in the resinencapsulant A, except for forming a resin composition using 55 grams ofRE 4045 and 59 grams of MHAC-P.

The resin encapsulant B had a glass transition temperature Tg of 170° C.and a shear strength of 3.8 MPa, which properties are inferior to thoseof the resin encapsulant A. This is probably because the resinencapsulant A gives a cured product containing a larger amount ofhydroxyl groups derived from the material biomass compound.

The resin encapsulant A was applied to a flip-chip ball grid array(FC-BGA) illustrated in FIG. 1.

In FIG. 1, the reference numerals “1” stands for a wiring circuit board,“2” stands for a gold plating, “3” stands for a gold bump (solder bump),“4” stands for a semiconductor device, “5” stands for a solder ball, and“6” stands for a resin encapsulant. The gold plating 2 of the wiringcircuit board 1 and the semiconductor device 4 are coupled to each otherthrough the gold bump 3. A gap between the wiring circuit board 1 andthe semiconductor device 4 was sealed by applying the resin encapsulant6 thereto and heating the applied resin encapsulant at 180° C. accordingto the capillary flow method. The gap was 100 μm and the pitch betweenbumps (intervals between the adjacent gold bumps 3) was 150 μm.

In this way, the resin encapsulant A was verified to be applicable toFC-BGA.

As a result of comparisons between the examples and comparativeexamples, the biomass-derived epoxy resins according to the presentinvention have both high glass transition temperatures (Tg: heatresistance properties) and satisfactory solubility in organic solvents.In addition, they have higher shear strengths than those of the knownequivalents.

1. A method for manufacturing a biomass-derived epoxy compound,comprising the steps of: dissolving a raw-material biomass-derivedcompound in an aqueous alkali solution, the raw-material biomass-derivedcompound containing at least a hydroxy group; adding epichlorohydrin tothe solution and heating the resulting mixture to a temperaturesufficient to epoxidize the raw-material biomass-derived compound;evaporating unreacted epichlorohydrin, water, and by-products from themixture, yielding a residue containing a biomass-derived epoxy compound;combining the residue with an alcohol; and precipitating thebiomass-derived epoxy compound, wherein the aqueous alkali solution hasa pH of 13.5 to 11.0.
 2. The method for manufacturing a biomass-derivedepoxy compound according to claim 1, wherein the aqueous alkali solutionis at least one selected from the group consisting of aqueous organicammonium solutions, aqueous alkaline earth metal salt solutions, andaqueous carbonate solutions.
 3. The method for manufacturing abiomass-derived epoxy compound according to claim 1, wherein theraw-material biomass-derived compound has a weight-average molecularweight of 300 to 10,000.
 4. The method for manufacturing abiomass-derived epoxy compound according to claim 1, wherein theraw-material biomass-derived compound is at least one selected from thegroup consisting of lignins and lignophenols.